STANFORD -- Satellites are easier to handle in space than on earth. And a
lot harder to control.

In the frictionless, free-fall environment of space, moving a huge
satellite requires no more than a push. Controlling its movement and guiding
it, however, creates immensely difficult problems for humans accustomed to
the dynamics of objects on Earth.

Stanford's aeronautics and astronautics department's Automated Robotics
Laboratory may have come up with a workable solution: robots that could build
space stations, rescue satellites and perform repairs on spacecraft.

The $12 million robot project, a joint venture of the Automated Robotics
Laboratory with NASA, plans to put a fully operational robot in space in
three to five years time.

In a lab designed to simulate space, Kurt Zimmerman, a doctoral student in
electrical engineering, demonstrated how the robot is to work in space. From
his computer terminal, he commanded the robot to "capture" another object.

The resulting show looks like a scene straight out of Star Wars. The robot
floats smoothly across a granite surface, following the target object. It
stretches its long arms; the probes at the end of the robot arm play a short
game of dodging with the slowly spinning target object; then two probes
latch on to predetermined spots on the object.

The robot will maneuver in space with the help of cold-gas thrusters.
Sensors will detect color patterns or a light source on "targets" like
satellites.

"After an astronaut points the robot in the direction of the target
satellite from a remote station, it will navigate its path in space using the
same satellite-guided Global Positioning System that American troops used
during the Gulf War," said Robert Cannon, Charles Lee Powell Professor of
Aeronautics and Astronautics and former chair of the aero/astro department.

Using information from 24 satellites stationed at different points in
space, the robot can compute its exact position in relation to a target
satellite.

Marc Ullman, an astronautical engineering student, built a two-dimensional
simulation of space in a basement room.

He moved a huge, smooth slab of granite into the lab. The robot then was
built to float over this surface. It levitated on an air pad three-
thousandths of an inch thick to simulate a two-dimensional form of zero-
gravity space.

"Moving the granite slab into the lab was harder than getting the robot to
'float' over it," Ullman said. "We had to take down a temporary wall to move
the 18-ton slab into the lab."

Ullman brought other talents as well to the research project. A cellist,
he developed the "theme music" for the video recording of the robot's glide
across the granite surface - a composition by the French composer Camille
Saint-Saens.

The project's potential applications include a drastic cut in costs, with
robots performing longer and better in space than can astronauts in rescuing
satellites or building space stations, said Ed Wilson, a mechanical
engineering student involved in developing neural network-based technology to
add onto the robot.

Robots in space also would mean fewer risks to astronauts and far less
spending on costly safety measures.

-jns/slug-

This story was written by Shankar Vedantam, a science writing intern at
the Stanford News Service.

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